Ab-initio Analysis of Phonon States in LPSO-type Mg Alloys

Several magnesium alloys include long period stacking ordered (LPSO) structures which consist of periodic arrangement of basal stacking faults and enrichment of solute atoms in the vicinity of the stacking faults. The solute-enriched layers give rise to a significant mass change as well as local stiffness due to the L12-type solute clusters, which affect the lattice vibration properties of the LPSO structures. Our previous study showed that for a heavy enough mass change, a phonon-mediated interaction of the solute-enriched layers is attractive and stabilizes the periodic stacking of the solute-enriched layers. In this study, we investigate detail phonon states of LPSO structures using first-principles calculations. We analyze phonon density of states and phonon dispersion based on the density functional perturbation theory.